CLN: Make engines.py flake8-able

Author: gfyoung

pandas/computation/engines.py

@@ -1,13 +1,11 @@
-"""Engine classes for :func:`~pandas.eval`
 """
-
-# flake8: noqa
+Engine classes for :func:`~pandas.eval`
+"""
 
 import abc
 
 from pandas import compat
-from pandas.compat import DeepChainMap, map
-import pandas.core.common as com
+from pandas.compat import map
 import pandas.formats.printing as printing
 from pandas.computation.align import _align, _reconstruct_object
 from pandas.computation.ops import (UndefinedVariableError,